When Google agreed to buy Zagat for $151 million nearly seven years ago, the technology giant intended to bring the restaurant review empire into the digital age.

Now ownership of Zagat will change again — into the hands of an upstart restaurant review company that has harnessed smartphone apps, an Instagram hashtag and a texting recommendation service as parts of its path to growth.

That company, The Infatuation, plans to announce on Monday that it has bought Zagat from Google. It did not disclose the amount.

“How often does an iconic brand like Zagat become available?” Chris Stang, a co-founder of The Infatuation and its chief executive, said in a telephone interview. “When you think about its history and what Zagat means to so many people, it’s a huge opportunity.”

The deal will bolster the profile of the nine-year-old The Infatuation. But it also raises questions about whether Zagat, once the 800-pound gorilla of restaurant recommendations, can remain relevant when a slew of younger digital competitors have emerged and thrived.

Founded by Tim and Nina Zagat as a survey of their friends’ opinions on New York City eateries, Zagat and its quotation-mark-laden reviews — appearing in the company’s distinctive burgundy-colored guidebooks — once made the publisher synonymous with searches for restaurants.

Then Google bought the company — under the direction of Marissa Mayer, who went on to become Yahoo’s chief executive — to integrate it into its mapping service. Life under Google has sometimes been rocky for the business, including a de-emphasizing of Zagat content in favor of Google’s own collected recommendations.

In 2016 Google unveiled a new look for Zagat’s website and an app that provided suggestions based on users’ locations and the time of day.

“Zagat has helped us provide useful and relevant dining results for users across our various products,” Jen Fitzpatrick, a vice president of product and engineering at Google said in a statement. “The Infatuation is an innovative company that will be a terrific home for the Zagat brand.”

Now Zagat’s future lies with a nine-year-old business founded by Mr. Stang and Andrew Steinthal, two former music industry executives who initially wanted a way to recommend restaurants and bars to their friends.

That side project eventually became The Infatuation, whose in-house team of reviewers covers restaurants in cities like New York, San Francisco, Los Angeles and London.

The company has succeeded in part by embracing technologies both new and old: It popularized “#EEEEEATS” as a branded hashtag on Instagram, and runs a slew of food-related accounts on the social network. It also rolled out Text Rex, a texting recommendation service staffed by humans to recommend eateries for users’ particular situations.

The company said it became profitable last year.

“We relate to audiences in a way that other entities aren’t,” Mr. Stang said. “We try to create a true connection with the audience.”

Nina Zagat said the deal would provide a healthy future for the company. “Tim and I are very excited for Zagat’s next chapter with The Infatuation,” she said. “Their innovative approach, and their passion for helping people discover great restaurants and for building community line up with what we built with Zagat from the very beginning.”

Though Zagat’s prominence has dimmed over time, Mr. Stang said that the brand remained relevant today, and that The Infatuation would apply its technological expertise to develop it further.

The company intends to keep Zagat as a separate brand, using it as a user-generated-content counterpart to The Infatuation. One possibility is integrating Zagat’s content into other products and platforms.

“We’re just trying to build something that takes this powerful brand and continues to grow it,” he said.